I have a Nexus 5 phone that normally works great. It's a FreedomPop phone which works on the Sprint network.
Here are some problems and solutions that I've discovered. These are applicable to most Android phones, not just the Nexus 5. Thanks to the contributors on various forums where I found these answers.
To stop excessive data usage on your Android phone:
Open Google Play Store and tap the menu button in the upper left (three horizontal lines). Tap Settings and look at the Auto-update setting. Is it set to update apps over wifi only? If not tap to change it. Do this for Google Services also.
My FreedomPop/Sprint network phone would sometimes stop connecting to Sprint's 3G (older) network. Sprint has a 3G (slower, but still works fine for things like Waze, Gmail) and a faster LTE network.
Here's a solution from a forum:
I had the same problem (no data at all using cellular network) ..., but managed to solve it using these steps:
Type star#star#4636#star#star in the phone dialer. You will see a rather messy dialog "Phone info".
Tap the three dots in the upper right corner and tap "Enable data connection".
Sometimes my phone would give me the message : Sign into Sprint Network.
Here's the solution: It's called a soft reset, and is for initial activation or if an Android phone says "Sign into Network": dial ##72786## and press the dial button
PS -- You might have to update the PRL and profile, and then restart the phone.
Update the Profile and PRL (Preferred Roaming List) on your Google Nexus 5
Keeping your Preferred Roaming List (PRL) up-to-date can improve your network coverage if you are roaming.
From the home screen, tap the All Apps icon.
Scroll to and tap Settings.
Tap Cellular networks.
Tap Carrier settings.
Tap Update Profile
After the update completes, tap Update PRL
Stop Excessive Data Usage:
For the FreedomPop Nexus 5 phone -- this phone had a problem specific to FreedomPop -- FP put a custom ROM on the phone, and the phone would constantly download updates to the Android OS (5.0) and then fail.
Here's the solution: I did the following to stop data usage from Android updates constantly uploading:
Go to Settings>>Data Usage>>Click "Google Services">> Scroll to the bottom and click "Restrict Background Data - Disable background data on cellular networks". Now your phone will stop downloading the Android 5.1 update until you uncheck this option. I also did this for Google Play settings -- set it to auto update apps over wifi only.
When I was on a boat in Papua New Guinea, I had a Nexus 4 with a local SIM in it. I had 1.5Gb of data which had to last me a month. I made the following settings so that apps would not suck up my data in the background:
1. Go to Settings>>Data Usage, and turn off Cellular Data by moving the green button to the left. Press OK to "Turn off cellular data?" This way, my phone would only update apps and use up data if I was near a wifi hotspot -- it would not use cellular data at all. When I was on the boat and had no wifi signal, I turned cellular data back on -- and the phone would update apps and get my Gmail over the cellular connection.
2. Another setting is found here: Go to Settings>>Data Usage, and tap the three dots in the upper right of the screen. Choose "restrict background data" and say OK to "Restrict background data? If you restrict background cellular data, some apps and services won't work unless you're connected to wifi." By doing this, you aren't allowing your phone to work in the background, updating apps and getting your emails -- unless the phone is hooked up to wifi.
If I chose setting 1 -- turning off cellular data -- the phone was basically not getting any data at all when I was at sea (the boat had no wifi), even if there was a cell phone signal. If I allowed cellular data but restricted background data, then I could pick up the phone if I was at sea with a cell signal, go to Gmail, and tell Gmail to get my emails. Gmail would not download my emails in the background -- it would only get my emails if I opened Gmail up and synced it.
Note: the DJI Go app sucks up data also, so setting it to get data only over wifi is a good idea.